The field of the present invention pertains generally to packaging for electronic components. More specifically, the present invention pertains to a device used to seal plastic containers for electronic components which includes an anvil and a heated shoe assembly.
Automating the process of making electronic circuitry necessarily includes presenting electronic components to a robot in a consistent, predictable orientation so that the robot may grasp the component and place it onto a circuit board. Requiring a robot to select and orient the components from a bin, for example, would be impractical, if not impossible. Even if the components are placed on the circuit board manually, presenting the components in a consistent, orderly fashion increases the productivity of the worker.
Proper packaging methods can ensure that the components are presented to an operator, assembler, or a robot in a predictable, repeatable manner. One such packaging method results in a string or xe2x80x9ctapexe2x80x9d of plastic pockets, each containing a component. This method includes a forming a strip of plastic into an elongate tape of pockets which are roughly centered between the longitudinal edges of the tape. The pockets do not extend all the way to the edges of the tape such that two horizontal flanges exist on either side of the pockets. The flanges run the length of the tape and provide a surface to which a cover sheet may be attached to secure the components within the pockets. An example of this type of packaging is shown in FIG. 1.
One manufacturing problem that this packaging presents pertains to the accuracy required by the machinery used to secure the covering sheet to the flanges. Whether the covering sheet is secured to the flanges with an adhesive or by heat sealing, a rigid surface below the flange and above the sheet are used to press the sheet and the flange against each other. The assembly above the flange is referred to as a shoe and the surface below is referred to as an anvil. Because the flange and the cover are extremely thin, there is little room for error in the alignment of the opposing rigid surfaces. If, for example, the surfaces are not completely parallel, one side of the rigid surface will be closer to its opposing counterpart than the other side. As the two rigid surfaces approach each other in a sealing operation, the closer side will make contact first, thereby pressing the cover and the flange together, but will prevent the other side from ever making contact and, thus, from forming a proper seal. The result will be a length of the tape wherein one side of the cover is secured and the other is not. If allowed to repeat, there will be produced a component tape having areas in which the cover is secured alternating with areas in which the cover is not secure.
There is a need for a anvil having flat surfaces which automatically assume an orientation which is parallel to the flat surface against which they are being pressed.
There is further a need for an improved anvil that obviates the need for periodic realignment.
There is a need for an improved heated shoe having operative surfaces which automatically assume an orientation which is parallel to the flat surface against which they are being pressed.
There is a further need for an improved heated shoe assembly that obviates the need for periodic realignment.
A xe2x80x9cfloatingxe2x80x9d anvil assembly is provided having a pair of inserts with two flat contact surfaces against which a heated shoe may be pressed. The inserts have a predetermined range of rotation about an axis such that when the shoe is pressed against each of the inserts, the contact surfaces of the inserts assume a parallel relationship with the contact surfaces of the shoes.
More specifically, the anvil assembly of the present invention generally comprises a base to which a pin is operably connected. A first and second insert are rotatable around the pin over a predetermined angular range. The base is preferably shaped like a horseshoe, opening upwardly, with the inserts positioned on the insides of, and adjacent to, the base side walls.
The flat contact surfaces of the inserts are constructed and arranged to act against a separate surface of the package sealing machine during a sealing operation. The upper surfaces preferably end slightly below the walls of the base so that the upper inside sides of the base walls may act against the sides of the packaging tape to maintain the alignment of the tape as it is fed over the inserts. The predetermined range of rotation is provided by the shape of the lower edges of the inserts. The lower edges of the inserts act against the bottom of the base during rotation, thereby defining the forward and rearward limits of rotation.
In operation, the anvil assembly is placed in a heat sealing machine and a packaging tape is fed over the inserts so that the flanges of the tape ride on the top surfaces of the inserts and the pockets of the tape extend between the inserts. A heated shoe having heated surfaces drops down and acts against the top surfaces of the inserts to press the cover sheet and the flanges of the tape together. The inserts may rotate slightly so that the top surfaces of the inserts are parallel to the heated surfaces of the shoe. The shoe remains pressed against the inserts for a predetermined period of time until enough heat is absorbed by the packaging to create a seal between the flange of the package and the covering sheet. The shoe is then lifted and the tape is advanced, guided by the walls of the base, and the process repeats.
The ability of the inserts to rotate slightly ensures that the pressure felt by the packaging will be substantially even across the extents of the upper surfaces of the inserts. If the inserts were fixed relative to the base, the inserts would have to be perfectly parallel to the surfaces of the packaging machine in order to accomplish placing even pressure across the extents of the inserts.
In an alternate embodiment, a floating shoe assembly is provided having a pair of independent shoes moveable along a single line or arc, each having a heated blade which presses against rigid contact surfaces of an opposing anvil. The blades have a predetermined range of rotation about an axis generally perpendicular to the line of movement of the shoe, such that when the blades are pressed against the contact surfaces of the anvil, the blades assume a parallel relationship with the contact surfaces of the anvil. The anvil and pair of shoe assemblies are configured to provide sealing to both sides of a tape in a manner similar to the embodiment described above.
More specifically, each shoe assembly of this embodiment generally comprises a pin operably connected to a shoe. The blade is rotatable around the pin over a predetermined angular range. The shoe is preferably shaped like a horseshoe, opening downwardly, with the blade substantially filling and extending from the opening of the horseshoe. The inner side walls of the horseshoe provide lateral support for the blade, along with the pin.
The pin and blade are constructed and arranged to provide a small space between the upper surface of the blade and the inner top surface of the shoe. This small space or gap provides the range of rotation for the blade. As it may be desired to place a heating element in the shoe as opposed to, or in conjunction with, the blade, for heating the blade, it is important that the gap be relatively small and that the width of the blade closely matches the width of the opening of the horseshoe. This arrangement maximizes surface to surface contact between the blade and the shoe, thereby increasing the heat transfer therebetween.
It is therefore an object of the present invention to provide an anvil assembly having contact surfaces which rotate to assume a parallel relationship with the heated surfaces of a shoe acting the anvil assembly.
It is further an object to provide an anvil assembly which obviates the need for realigning a packaging machine on a regular basis.
It is also an object to provide a shoe assembly having rotatable blades for acting against a fixed anvil.
These and further objects and advantages of the present invention will become clearer in light of the following detailed description of illustrative embodiments of this invention described in connection with the drawings.